The Relationship Between Anterior Alveolar Morphology And Vertical Facial Type In Adult Chinese Patients With Bimaxillary Dentoalveolar Protrusion

Objective:This study focused specifically on CBCT measurement of alveolar bone overlying healthy maxillary and mandibular central incisors to research the anterior alveolar morphology and its relationship with vertical facial type in adult Chinese patients with bimaxillary dentoalveolar protrusion.Methods:Forty-eight (Age,23.5±1.0years;24males,24females) adult bimaxillary dentoalveolar protrusive patients were included in this study. All the subjects were taken corn beam tomography (CBCT) scans and lateral cephalograms. Three facial types consisting of hypodivergent group, normodivergent group and hyperdivergent group were formed based on the Frankfort-mandibular angle and S-Go/N-Me. After that the CBCT scans were transferred to Mimics10.01software (Materialism’s interactive medical image control system, Materialise, Belgium), measurements were taken on mid-sagittal sections of both the upper and lower central incisors. Sixteen parameters defining the labio-lingual inclination of incisor and alveoli, the alveolar height, the alveolar thickness and the distance from the root apex to the cortex were measured. One way analysis of variance and Student-Newman-Keuls tests were performed to check the differences among the three facial types.Results:1. At the maxillary central incisors, the hyperdivergent subjects showed significantly thinnest lingual alveolar thickness and shortest distance from root apex to lingual cortex, the hypodivergent subjects showed significantly thickest lingual alveolar thickness and farthest distance from root apex to lingual cortex, the normodivergent subjects yielded an intermediate value (P<0.05)2. At the mandibular central incisors, the lingual alveolar thickness was found to be thinnest and the distance from root apex to lingual cortex was found to be the shortest in the hyperdivergent group (P<0.05). No significant differences were found among the normodivergent and the hypodivergent groups concerning the lingual alveolar thickness and the distance from root apex to lingual cortex.3. No significant differences were found among the hyperdivergent, normodivergent and the hypodivergent groups concerning the inclination of the central incisor, the alveolar height, the labial alveolar thickness, the distance from the root apex to labial cortex, the distance from the root apex to palatal plane or to the mandibular plane.4. The labio-lingual inclinations of the labial alveoli at the upper central incisors were found to be greater, and the labio-lingual inclinations of the lingual alveoli at both the upper and lower central incisors were found to be smaller in the hyperdivergent group (P<0.05).Conclusion:There is significant correlation between vertical facial type and anterior alveolar morphology in adult patients with bimaxillary dentoalveolar protrusion. When the Frankfort-mandibular angle becomes larger or the labio-lingual inclination of the central incisor becomes greater, the associated lingual alveolar bone becomes thinner.